Between Christmas and the new year, my son, my two grandsons and I made a visit to Andrew Mawson, this was the third annual visit for my son and I. It's fun to visit other madmodders, put a face to a name and see some of the things that have been the subject of forum threads! All three generations enjoyed themselves and I was followed home by the thirty five year old Warco mechanical hacksaw Andrew had offered it to me last year, but I was on my motorbike, so getting it back across the channel would have been a little tricky!. The aforementioned saw had spent the last seven years outside. I finally was able to get it out of the van and into my workshop. The light failed me so I wasn't able to get many photos. Nothing was seized, and the drive belt wasn't even cracked, amazing! It looks as though the original threads on this thirty five year old Taiwanese knock off are Unified, Andrew said that he had bought it from a blacksmith when it was about ten years old, so that might have been when it picked up the Whitworth replacements for the UNC bolts! I'm not going to restore it, just make it work. I found a switch for $6 from Hongkong and ten replacement blades on eBay for 25€, so far, I can't see anything else apart from the plug and the oil to replace!

Matthew, I have a very dim recollection that there was an adjuster on the dash pot system that worked by screwing a pointed bar against an orifice to regulate the rate of oil flow for descent. That thing does two things - it raises the blade off the work on the return stroke and controls the rate of descent on the forward cutting stroke. It's the rate of descent that was adjustable but I'm puzzled that I see no sign of the tweaker

Andrew,I wondered about that, there is a screw opposite the "exhaust" port on the small dash pot, but it doesn't go very far. It's a really clever mechanism that works just with the pistons and oil ports, really neat! From what I remembered of the one we had in school over fifty years ago, seeing the system made my memories of it lifting on the return stroke come back. I know I'm going to enjoy having the Warco, it's got the same sort of attraction when running as a shaper!

[you tube][/you tube](note: I've added spaces so it shows up properly in this post...)

Now all you need to do is paste your video's unique code between the two tags, and you're golden! The code appears in the URL (address bar in your browser), just click on it and it should show up in full. Or, once the video has finished playing, copy the code out of the "share" box (see attached picture).

Thanks AdeVI think this should be a sticky! Thank you for going to the trouble of explaining it so clearly! Those icons above all that animated stuff never read as being anything usable! I fail to see why that function is not part off attachments. It's obvious when you look at it, especially as I know how html code works!

[you tube][/you tube](note: I've added spaces so it shows up properly in this post...)

Now all you need to do is paste your video's unique code between the two tags, and you're golden! The code appears in the URL (address bar in your browser), just click on it and it should show up in full. Or, once the video has finished playing, copy the code out of the "share" box (see attached picture).

Hermetic, I chose to drill the plug rather than trying to get it out because I could see that the drilling for the oil ways was pretty small so I thought that it would be worth the minimal risk and that I could always plug it!!

Here is the video of making an anti return valve for the hydraulic down feed system!

I'm sure that the down feed of the hacksaw was originally tweakable with some sort of variable throttle on the oil escaping from the big pot, and the little pot is pumped by a cam that raises the saw on the reverse stroke.

(Can I respectfully suggest a couple of things? a/ put loctite on your grub screw that retains the spring (or centre pop it) and b/ use a board under your work when sawing in the lathe to preserve the ways - I've seen too many ex-school lathes with saw nicks in them )

I'm sure that the down feed of the hacksaw was originally tweakable with some sort of variable throttle on the oil escaping from the big pot, and the little pot is pumped by a cam that raises the saw on the reverse stroke.

(Can I respectfully suggest a couple of things? a/ put loctite on your grub screw that retains the spring (or centre pop it) and b/ use a board under your work when sawing in the lathe to preserve the ways - I've seen too many ex-school lathes with saw nicks in them )

Thanks Andrew,

Yes, your absolutely right about the plank on the ways, I usually do!! The grub screw can't escape, it's up against the bottom of the hole, it's there to stop the spring falling out when it's being installed! I've been all over the reservoir, there no threaded holes that I can see that could have contained an adjuster screw. The only port into the larger chamber is through the bottom, the small piston has a hole half way up it's stroke which vents oil to the reservoir, in doing so it allows oil to escape from the large cylinder, which allows a drop in the height of the blade! I'd love to find an adjuster screw! The adjustment seems to come from the screw that adjusts the stroke of the small piston following the cam. I am still cleaning and painting, it'll be clearer when it's back together!

Matthew, I vaguely looked into this about 15 !years ago - I saw a very similar Taiwanese saw in a used tool dealer, and there was a knurled knob on the end of a shaft emerging from the hole in the top plate that you used as a jig for drilling

I suspect that there was a ball valve similar to yours, but with something pressing on the ball to give a controlled leak. If you think about it, if your ball valve is perfect, the blade will never descend ! The little cylinder just transfers enough oil into the bigger one to lift the blade off the cut on the return stroke, but re-admits in on the forward stroke controlled by the timing of the cam.

Matthew, I vaguely looked into this about 15 !years ago - I saw a very similar Taiwanese saw in a used tool dealer, and there was a knurled knob on the end of a shaft emerging from the hole in the top plate that you used as a jig for drilling

I suspect that there was a ball valve similar to yours, but with something pressing on the ball to give a controlled leak. If you think about it, if your ball valve is perfect, the blade will never descend ! The little cylinder just transfers enough oil into the bigger one to lift the blade off the cut on the return stroke, but re-admits in on the forward stroke controlled by the timing of the cam.

Happy experimenting

That is what I'd thought, but, there were no traces of anything in and around the hole, no threads, no signs of anything! The one thing that is certain, a ball valve is required to allow the oil in. The small piston rises and falls, pressurising the large chamber raising the blade. The cam then allows the blade to lower, by venting partially the large cylinder through the port in the small cylinder. that much is clear, the thing that is not clear for me, which may have to do with the nob is lowering the blade down to the working position!

At a conceptual level you need a needle valve in parallel with your ball valve introducing a 'controlled leak' adjusted from a rod though the hole in the lid. How you implement it might be a bit more complicated.

Thanks Andrew, I can see a way of doing it, a needle that can apply pressure to the ball valve from the top. I need to experiment when I get it back together. There is one thing that I need to confirm before I do anything else, it's the flow of oil when the saw is on the cutting stroke. On the return stroke, the small piston goes down, sending oil to the big piston pushing up the arm. When the blade reaches the end of it's stroke, the cam allows the small piston to rise (under pressure from the weight of the arm pushing the piston down) uncovering the port on the side of the small cylinder (it's about half way up) which lets the oil out of the large cylinder allowing the arm to drop, the port is open throughout the cutting stroke. At least that's what I can see so far! The saw in the video doesn't have anything on the to of the cover. I've written to the poster in the Madmodder's thread on rebuilding the mechanical hack saw, it would be easier to have something concrete to work from!

2nd opinion, well, it was a really great gift from Andrew Mawson, I'm pleased to have it, looking forward to it running!

Krv, The compact 8 is really useful, it's in really good shape, it was missing the motor when I got it, it came out of a school, apparently the kids had deliberately locked the motor an left it running and burnt it out. It still had the "cosmolene" on the bed ways! It's a real complement to my other big lathes!

Thanks for the offer, I have a three phase motor (from a V10 Emco I think) that cost me €70 shipping from Australia! It's a three phase, two speed that I mounted with a three to one reduction on a lay shaft with a toothed timing belt. I Also put a 1 to 1 gearing option, which I've never used as I've never needed it! It'll run as slow as 33 RPM which I find great for threading up to a shoulder!

In the good old days, motor cycle oil pressure relief valves were just a ball bearing pressed by a spring against a cast iron bored hole. The received wisdom (written into maintenance handbooks) was to put a bronze drift against the ball, and give it a firm clout with a hammer, thus deforming the seat to the sphericallity of the ball. Those of us without bronze drifts used a steel rod, then replaced the ball bearing with another identical one, and it seemed to work splendidly. (no lapping allowed as the oil galleries would become contaminated)